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Christoph Eckert | 11 May 2011 23:49
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[MoNav Dev] Precision of UnsignedCoordinate::ToGPSCoordinate()

Hi,

compared to Mappero, which provides lat and lon with 6 decimal digits, I get 
only 4 digits for lat and 5 digits for lon from MoNav - which is a bit 
inaccurate.

I have no clue whether this is caused by QGeoPositionInfoSource or my 
own/MoNav's code:

const RoutingLogic::GPSInfo& gpsInfo = RoutingLogic::instance()->gpsInfo();

qDebug() << gpsInfo.position.x << gpsInfo.position.y;
qDebug() << gpsInfo.position.ToGPSCoordinate().latitude \
<< gpsInfo.position.ToGPSCoordinate().longitude;

results in something like

561900976 368759099 
48.9973 8.39198 
561900931 368759164 
48.9973 8.39197 
561900925 368759161 
48.9973 8.39197 
561900891 368759111 
48.9973 8.39195 
561900852 368759081 
48.9973 8.39194 
561900862 368759041 
48.9973 8.39194
(Continue reading)

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Christian Vetter | 12 May 2011 00:00
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Re: [MoNav Dev] Precision of UnsignedCoordinate::ToGPSCoordinate()

Hi,

On Wed, May 11, 2011 at 11:49 PM, Christoph Eckert <ce <at> christeck.de> wrote:
> Hi,
>
> compared to Mappero, which provides lat and lon with 6 decimal digits, I get
> only 4 digits for lat and 5 digits for lon from MoNav - which is a bit
> inaccurate.
>
> I have no clue whether this is caused by QGeoPositionInfoSource or my
> own/MoNav's code:
>
> const RoutingLogic::GPSInfo& gpsInfo = RoutingLogic::instance()->gpsInfo();
>
> qDebug() << gpsInfo.position.x << gpsInfo.position.y;
> qDebug() << gpsInfo.position.ToGPSCoordinate().latitude \
> << gpsInfo.position.ToGPSCoordinate().longitude;

The reduced accuracy is only caused by the output. qDebug outputs with
a default accuracy of 6 digits ( including  the ones before the
decimal point ).  So you have to increase the floating point accuracy
of whatever output functions you are using. I do believe that qDebug
cannot be modified to output with increased accuracy. However, you can
use QString().arg(...) (
http://doc.qt.nokia.com/latest/qstring.html#arg-20 ).

UnsignedCoordinate itself should be accurate to at least 4cm ( worst
accuracy on the equator ). The conversion from GPS to
ProjectedCoordinate transforms the coordinate into the Mercator
projection used by OSM, x in [0,1], y in [0,1]. This is beneficial
(Continue reading)

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Christoph Eckert | 12 May 2011 00:15
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Re: [MoNav Dev] Precision of UnsignedCoordinate::ToGPSCoordinate()

Hi,

> The reduced accuracy is only caused by the output. qDebug outputs with
> a default accuracy of 6 digits ( including  the ones before the
> decimal point ).  So you have to increase the floating point accuracy
> of whatever output functions you are using.

I've seen this in the tracklog, using QString::number(). Increasing its 
precision to 6 digits only gave me additional 0's. Based on your hint, I'll 
try anew. In case the problem persists, I'll come back with some more details.

BTW: I've added a first german translation to the uing branch. Except for some 
minor hickups, it looks great on the N900 and the desktop so far.

Gn8,

ce
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Christoph Eckert | 13 May 2011 23:07
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Re: [MoNav Dev] Precision of UnsignedCoordinate::ToGPSCoordinate()

Hi,

> The reduced accuracy is only caused by the output. qDebug outputs with
> a default accuracy of 6 digits ( including  the ones before the
> decimal point ).  So you have to increase the floating point accuracy
> of whatever output functions you are using. I do believe that qDebug
> cannot be modified to output with increased accuracy. However, you can
> use QString().arg(...) (
> http://doc.qt.nokia.com/latest/qstring.html#arg-20 ).

thanks a bunch for the pointer. Of course "it was all my fault" - the 
precision obviously went down as I had the device on my desk…

Outdoors, either of the following provide the desired results:
double latitude = m_gpsInfoBuffer.at(i).position.ToGPSCoordinate().latitude;

std::cout.precision( 6 );
cout << latitude;

QString::number( latitude, 'f', 6 )

I apologize for the traffic, but at least we now have more accurate logging for 
MoNav :) .

--

-- 
Beste Grüße,
Best regards,

ce
(Continue reading)

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Christian Vetter | 14 May 2011 03:22
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Re: [MoNav Dev] Precision of UnsignedCoordinate::ToGPSCoordinate()

Hi,

Glad that's fixed. I already fell into that trap several times myself
when coding GPS loggers.

Regards,

Christian Vetter

On Fri, May 13, 2011 at 11:07 PM, Christoph Eckert <ce <at> christeck.de> wrote:
> Hi,
>
>> The reduced accuracy is only caused by the output. qDebug outputs with
>> a default accuracy of 6 digits ( including  the ones before the
>> decimal point ).  So you have to increase the floating point accuracy
>> of whatever output functions you are using. I do believe that qDebug
>> cannot be modified to output with increased accuracy. However, you can
>> use QString().arg(...) (
>> http://doc.qt.nokia.com/latest/qstring.html#arg-20 ).
>
> thanks a bunch for the pointer. Of course "it was all my fault" - the
> precision obviously went down as I had the device on my desk…
>
> Outdoors, either of the following provide the desired results:
> double latitude = m_gpsInfoBuffer.at(i).position.ToGPSCoordinate().latitude;
>
> std::cout.precision( 6 );
> cout << latitude;
>
> QString::number( latitude, 'f', 6 )
(Continue reading)

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Gmane